Recently, a standard that is referred to as DVI has been standardized for transmitting video data to a display unit in digital format when a video signal source such as a television tuner, a video player, or a personal computer device is connected to a video display unit such as a monitor receiver.
Details of the DVI standard are given in an embodiment which will be described later, but in brief, this DVI standard digitizes respective primary color signals R, G, and B of video data in units of pixels and transmits the digitized data to a display unit, thereby realizing transmission and display of high quality pictures. Further, the display unit can directly drive a display driver by the received video data in units of pixels, thereby achieving the display with a relatively simple processing structure.
However, since a cable which is defined according to the DVI standard basically transmits only video data, then when audio data are to be transmitted together with video data, the display unit should be connected to an audio output device such as a tuner, through an audio cable that is different from the DVI standard cable.
More specifically, considering a system configuration that transmits only video data, a video signal source 600 and a display unit 610 are connected with a DVI standard cable 620 as shown in FIG. 30, and video data that is encoded in accordance with the DVI standard is transmitted through the cable 620, whereby video data can be transmitted from the video signal source 600 to the display unit 610.
On the other hand, when video data and audio data are transmitted from a video/audio signal source 700 to a display unit 710 with speakers as shown in FIG. 31, the video/audio signal source 700 and the display unit 710 with speakers are connected by a DVI standard cable 620 and an audio signal cable 630 that is different from the cable 620, and the video data is transmitted through the DVI cable 620 while the audio data is transmitted through the audio signal cable 630. In this way, the video data that is outputted from the video/audio signal source 700 can be displayed on the display unit 710 with speakers while the sounds are outputted from speakers 711 and 712 that are attached to the display unit 710.
However, when the video data and the audio data are transmitted from the video/audio signal source 700 to the display unit 710 using the two separate cables for video data and audio data as shown in FIG. 31, the connection structure correspondingly becomes complicated. Therefore, it is more preferable that fewer cables should be used for connecting the devices.
As a technology of multiplexing video data and audio data to transmit the multiplexed data through one cable, a data transmission technology using a bus line has been conventionally standardized as IEEE (The Institute of Electrical and Electronics Engineers) 1394 scheme. When a bus line that is standardized according to IEEE1394 method is employed as a cable for connecting the devices, video data and audio data can be simultaneously transmitted through one cable. However, in order to perform data transmission using the IEEE1394 bus line, very complicated data processing is required, whereby a structure on a transmitting end for encoding data to be transmitted, or a structure on a receiving end for decoding data that is received via the bus line needs quite a large circuit construction, resulting in an increased cost.
Further, since the IEEE1394 method compressively encodes and multiplexes video data and audio data in view of the transmission rate or the like, the quality of picture is lower than the above-mentioned DVI standard that transmits only video data which is digitized in units of pixel.
When digitized audio data is to be transmitted together with video data, a clock for audio data should be transmitted together with a clock for video data, and accordingly a signal line for transmitting the audio clock is required. Further, as a high-speed signal is transmitted through the signal line for the audio clock transmission, jitter is adversely increased.
The present invention is made to solve the above-mentioned problems, and has for its object to provide a data transmitter that transmits audio data and data for generating an audio clock from a transmitting end using an existing interface for transmitting video data, and a data receiver that receives the audio data and the data for generating an audio clock, and generating the audio clock easily and satisfactorily, to reproduce the audio data on a receiving end using the existing interface.